G-77/HLCST/2002/5
Safe Drinking Water:
The Need, the Problem, Solutions and Action Plan
Report prepared by the Third World Academy of Sciences
Report of the
Third World Academy of Sciences
The need, the problem,
solutions and an action plan
Safe
Drinking
Water
Safe Drinking Water
The need, the problem, solutions and an action plan
Report of the Third World Academy of Sciences
The Third World Academy of Sciences (TWAS) is an international
autonomous scientific organization dedicated to promoting scientific capacity
and excellence for sustainable development in the South.
TWAS was founded in Trieste, Italy, in 1983 by a group of distinguished
scientists from the South under the leadership of Nobel laureate Abdus Salam
of Pakistan, and officially launched by the then-secretary general of the United
Nations, Javier Perez de Cuellar, in 1985. The Academy’s operational expenses
are largely covered by generous contributions from the Italian government.
Since 1986 TWAS has supported scientific research in 100 countries
in the South through a variety of programmes. More than 2,000 eminent
scientists world-wide, including TWAS members, peer review proposals freeof-charge for research grants, fellowships and awards that are submitted to
the Academy by scientists and institutions from developing countries.
©
2002
Third World Academy of Sciences
Strada Costiera 11
34014 Trieste, Italy
phone +39 040 2240-327
fax +39 040 224559
email [email protected]
web www.twas.org
Safe Drinking Water
The need, the problem, solutions and an action plan
Contents
Foreword
4
Summary
7
Background
8
Ways to save and replenish
9
Making water safe and potable
12
Simple ways to succeed: Some national examples
13
Making wastewater fit for use again
15
Technologies to make safe drinking water
17
Action plan
21
3
Foreword
The Third World Academy of Sciences (TWAS) has earned a reputation as
one of the world’s foremost organizations for the promotion of science in the
developing world. This reputation is based largely on the worldclass research
conducted by its more than 600 members. This reputation is also based on
the Academy’s annual awards, grants, and fellowships, given to young scientists
from the developing world that have become among the most important
sources of scientific capacity building in the South.
While TWAS continues to nurture and expand its roots in the basic
sciences, it has increasingly examined how it might apply the scientific
expertise of its members to the South’s most pressing environmental,
economic development and health problems.
Much of the Academy’s work in this area has been conducted in close
partnership with the Third World Network of Scientific Organizations
(TWNSO) and is best represented by a series of monographs on best practices
that has been published in cooperation with other international organizations,
including the United Nations Development Programme’s (UNDP) Special
Unit for Technical Cooperation among Developing Countries (TCDC), the
United Nations Environment Programme’s (UNEP) Global Environment
Facility (GEF) and the World Meteorological Organizations (WMO). The
initiatives have focused on such issues as the conservation and wise use of
medicinal and indigenous plants, the protection of biodiversity in arid and
semi-arid regions, and the management of water resources in the developing
world.
This report, “Safe drinking water: The need, the problem, solutions
and an action plan,” is both an expansion and narrowing of focus of the
Academy’s larger efforts to put science to work in meeting critical human
needs in the developing world. It is an expansion because the Academy, for
the first time on its own, is moving beyond its traditional focus on capacity
building within the scientific community to applications of science in the larger
society, especially applications to address pressing environmental and public
health issues in the developing world. And it is a narrowing of focus, in the
sense, that this volume, unlike our previous volumes produced in cooperation
with TWNSO and its partners, largely avoids examining matters of policy and
administration. Instead it concentrates on effective science-based strategies
that have improved both water supplies and water quality in the communities,
nations and regions that have adopted them.
Indeed there may be no more critical problem facing the South than
securing adequate supplies of clean drinking water. As the following text makes
clear, it is a problem that demands our immediate attention because, if
4
neglected, it could have serious consequences for the health and well-being
of billions of people. In fact, if today’s clean drinking water problems are left
unresolved, all other policy initiatives designed to promote sustainable
development will likely fail because it is virtually impossible to envision future
generations of adequately fed and reasonably healthy people in the South,
particularly the arid South, unless we successfully attend to our current
problems in ensuring adequate supplies of clean water.
As revealed in the report, the good news is that science-based strategies
for attaining adequate supplies of clean drinking water have been put in place
in many parts of the developing world. Such strategies could be readily adopted
by others through concerted efforts designed to promote an exchange of
information among experts and policy officials and sustained programmes to
increase public awareness. This report is intended in large measure to facilitate
such efforts.
Part of the wonder of science will always lie in laying the groundwork
for what lies ahead. And part of the unmistakable value of science will always
lie in showing the rest of the world what can be done to improve the conditions
of all people, especially those who have been marginalized by circumstances
beyond their control.
This volume speaks to the latter concern and does so in a language that
we hope will achieve its ultimate goals: to increase public awareness about
the nature of the problem and, equally important, to describe what can be
done about it –now. This monograph, moreover, will form the basis of a more
comprehensive study that TWAS plans to undertake with other academies
and research organizations in the near future.
I would like to thank Dorairajan Balasubramanian, director of research,
L.V. Prasad Eye Institute, Hyderabad Eye Research Foundation, Hyderabad,
India, for his efforts in conducting the research and writing the draft
manuscript. I would also like to thank Daniel Schaffer, public information
officer for the Third World Academy of Sciences, Trieste, Italy, for his editorial
help in preparing the final draft for publication. We welcome your comments
and suggestions – both large and small – as the Academy moves ahead in
addressing this and other critical economic, environmental and health issues.
C.N.R. Rao, President
Third World Academy of Sciences
July 2002
5
Safe Drinking Water
The need, the problem, solutions and an action plan
Summary
Safe drinking water is the birthright of all humankind – as much a birthright
as clean air. The majority of the world’s population, however, does not have
access to safe drinking water. This is certainly true in most parts of Africa and
Asia. Even in relatively advanced countries such as India, safe drinking water
is not readily available, particularly in rural areas. One reason safe drinking
water is of paramount concern is that 75 percent of all diseases in developing
countries arise from polluted drinking water. Knowledge about how to make
water safe for consumption is rare in most developing countries. We simply
must do a better job of raising public awareness and understanding about the
nature of the problem and the technologies and strategies that are available
to address it.
The following document describes some of the best methods for
purifying water inexpensively. The conclusion is encouraging: Appropriate,
locally based, strategies can be devised to obtain safe drinking water in many
different parts of the developing world. To this end, we hope the document
proves useful.
We also plan to prepare a ‘user friendly’ version of this document in the
form of a poster or a pamphlet. These publications will be publicized through
our network of scientific academies and other organizations in developing
countries. Each developing country could produce suitable material in local
and national languages and develop other programmes to engage and educate
the public. If we spark the interest of all concerned, we may indeed make
progress in solving one of the most critical problems facing humankind.
7
Safe Drinking Water: The need, the problem, solutions, and an action plan
Background
Safe drinking water is a human birthright – as much a birthright as clean air.
However, much of the world’s population does not have access to safe drinking
water. Of the 6 billion people on earth, more than one billion (one in six) lack
access to safe drinking water. Moreover, about 2.5 billion (more than one in
three) do not have access to adequate sanitation services. Together, these
shortcomings spawn waterborne diseases that kill on average more than 6
million children each year (about 20,000 children a day).
Water covers 70 percent of the globe’s surface, but most is saltwater.
Freshwater covers only 3 percent of the earth’s surface and much of it lies
frozen in the Antarctic and Greenland polar ice. Freshwater that is available
for human consumption comes from rivers, lakes and underground sources
and aquifers. Together these sources account for just 1 percent of all water
on earth.
Six billion people depend on this supply and a significant portion of the
world’s population now face water shortages. Today 31 countries representing
2.8 billion people, including China, India, Kenya, Ethiopia, Nigeria and Peru,
confront chronic water problems.
Within a generation, the world’s population will climb to an estimated
8 billion people. Yet, the amount of water will remain the same. The challenge
is as clear and compelling as pristine water cascading down a mountain stream:
We must find new and equitable ways of saving, using and recycling the water
that we have.
Fig. 1 Water availability
Abundant
12345
12345
12345
Limited
12345
12345
12345
12345 Prone to severe shortage
Scarce
Stressed
8
Ways to save and replenish
The problem is not a lack of freshwater;1 indeed plentiful freshwater
resources are available in Latin America, the Caribbean, sub-Saharan Africa,
Europe and Central Asia. Water resources, moreover, do not correlate with
the level of economic activity within countries. The Congo has huge freshwater
resources – 291,000 cubic metres per capita. Papua New Guinea has 170,000
cubic metres per capita. The United States, meanwhile, has just 9000 cubic
metres per capita and Kuwait only 75 cubic metres per capita.
Unequal access. Access to safe water varies both among and within nations.
For example, 77 percent of city and town dwellers in the Congo have access
to safe drinking water but only 17 percent of rural inhabitants do. In the Lao
Peoples’ Democratic Republic, the situation is reversed: Virtually all rural
Laotians have access to safe drinking water but only 60 percent of the residents
in the capital city of Vientiane do.
Use of freshwater resources varies from one country to another. In lowincome countries, almost 90 percent of freshwater is used for agriculture, 8
percent for industry and only 5 percent for households. In high-income
countries, industry uses 59 percent, agriculture 30 percent and households
just 11 percent.
Two key factors lie at the centre of global concerns for the future
availability of freshwater, particularly safe drinking water. First, total
withdrawals of freshwater have increased dramatically in recent times. In fact,
withdrawals have doubled over the past 40 years. As a result, groundwater
aquifers are currently being depleted faster than they are being replenished
in parts of India, China, and the United States. Inefficient irrigation practices
that have played such a large role in groundwater depletion not only waste
water but degrade soil quality and reduce farm productivity, placing the
progress of the ‘green revolution’ at risk.
The second key factor of concern has been the relentless rise in
population in various parts of the world, particularly in developing countries.
Global population is expected to increase by 1.5 billion over the next 25 years
(reaching some 8 billion people by 2025). If this population increase comes
to pass, the amount of available freshwater per person per year will drop 40
percent – from more than 8000 cubic metres to about 5000 cubic metres.
Ways to save and replenish
We must meet the world’s growing demand for freshwater. However, we must
do so with limited financial resources and with practices that minimize
1
Freshwater resources refer to total renewable resources such as rivers, groundwater and rainfall.
9
Safe Drinking Water: The need, the problem, solutions, and an action plan
ecological disruption. Analyses of the situation suggests that our goals can be
reached. Experts have proposed a four-fold path towards a viable solution for
making water both potable and safe:
• Seek new sources.
• Save and redistribute supplies.
• Reduce demand.
• Recycle.
Some of these approaches are global in nature, while others are regional,
national, local and even family-specific. These efforts will ultimately succeed
only when we empower people with the knowledge and means to address
the issue on their own.
Seek new sources. As we seek new sources, it is important to note that
extracting freshwater from ocean saltwater is a time-honoured technique that
can be further advanced through the development of new, energy-efficient
methods of desalinization based on reverse osmosis. Earlier methods of
heating, evaporating, condensing and then collecting the resulting freshwater
proved too expensive for widespread use.
Reverse osmosis, however, represents a much cheaper, more energyefficient, alternative. In reverse osmosis, a thin, semi-permeable membrane
is placed between a container of saltwater and a container of freshwater. The
saltwater is subject to high pressure, pushing the water molecules across the
membrane into the freshwater container. The material comprising the
membrane allows water to pass while leaving the salt and impurities behind.
Development of sturdy, chemical-resistant membranes – made of thin,
composite polyamide films that can last for 10 years – has made reverse
osmosis an increasingly attractive and cost-effective technology for large-scale
extraction of freshwater from the sea. Today less than 1 percent of the world’s
drinking water comes from the sea, but with advances in reverse osmosis,
the percentage is likely to grow.
Redistribute. The second pathway for making water both potable and safe
involves saving and redistributing water supplies in ways that enable supplies
to reach those who need it in a waste-free and inexpensive manner. This
strategy seeks to save existing sources, not to develop new ones. The simple
act of plugging leaks from tanks, pipelines and taps can save large quantities
of water. Peter Gleick, a water expert who is president of the Pacific Institute
for Studies in Development, Environment, and Security, in the United States,
estimates that water lost from Mexico City’s leaky supply system, which serves
17 million people, would be enough to meet the needs of 3 million people. In
10
Ways to save and replenish
many countries, more than 30 percent of the domestic water supply is lost to
porous pipes, faulty equipment, and poorly maintained distribution systems.
Periodic repair and upgrade of these systems, combined with modest
modifications in domestic water facilities (for example, installing reducedvolume flush toilets), could make substantial amounts of water, which are
currently wasted, available for consumption.
Many communities worldwide have harvested rainwater for centuries.
However, this practice has waned in recent years for a variety of reasons,
most notably the crowding of people into tenements, apartment blocks and
group housing as part of the response to incessant population growth. Given
current and looming shortages in water supplies, time-tested methods of water
harvesting should be revived and encouraged. Many nations have pursued
this path with great success. Several water harvesting case studies, detailed
below, highlight one of the most eco-friendly and energy-efficient methods
for meeting the water needs of large populations.
Reduce demand. The third path for ensuring adequate supplies of safe
drinking water focuses on reducing demand. In developing countries,
agricultural practices place the highest demand on water, accounting for nearly
90 percent of all water consumption. In developed countries, industry, which
accounts for about 60 percent of all consumption, is the largest user. In both
the North and South, domestic needs represent less than 15 percent of total
water withdrawals. As these percentages show, reductions in demand for
water must come from the agricultural and industrial sectors. The good news
is that newer and more water-efficient processes for both of these sectors
have been developed over the past 50 years. For example, the amount of
water used in the production of one ton of steel has declined sharply from 80
tons in the 1950s to six tons today. Replacing steel with aluminium, other
alloys and plastics (for instance, in the automobile industry) has reduced
industry’s need for water even more.
Traditional agriculture worldwide, particularly for the cultivation of rice
and wheat, has been characterized by water-guzzling practices. For many farm
commodities, minor improvements in agricultural efficiency could substantially
reduce the demand for water without compromising the quality or size of the
yield. Innovative water-saving methods (discussed below), which have been
adopted in many countries, could serve as models for others to follow.
Recycle. The fourth path to a more secure water future lies in recycling. The
dictum here is ‘waste not, want not.’ Terrace farming, practiced in many hillside
communities throughout the world, may be the simplest example of effective
water recycling and multiple use. In terraced farming, water flowing from the
11
Safe Drinking Water: The need, the problem, solutions, and an action plan
higher terrain is not drained but is used to irrigate plants in the lower terrain.
Even wastewater or sewerage can be – and has been – processed and recycled
for use.
The reed-bed system (fig. 2), used in many countries, represents an
eco-friendly way of treating polluted wastewater for reuse. Such diverse
countries as Israel, Namibia, India, and Singapore practice recycling. Even
when circumstances make it difficult to recycle wastewater, ‘grey’ water can
be used to recharge groundwater. Such practices help curb salinity levels,
raise the water table in aquifers, and improve the ecological health of wetlands
or sanctuaries.
Fig. 2 Reed-bed recycling system
Inlet from
sedimentation
tank
Outlet
Roots of acclimated plants
in proprietary filling media
Making water safe and potable
How should we apply the technologies and strategies described above to
make drinking safer and more potable around the world?
Safe drinking water must be among the highest priorities for every nation
on earth. Today contaminated water kills more people than cancer, AIDS,
wars or accidents. It is vitally important that the water which humans drink
be free of disease-causing germs and toxic chemicals that pose a threat to
public health.
Moreover, given that more than 80 percent of the world’s population
lives in developing countries, technologies for making drinking water safe
12
Simple ways to succeed: Some national examples
must be accessible, affordable, environmentally sound, and tailored to a
nation’s cultural norms.
Technological options fall into two broad categories – those used by
municipal authorities at centralized points from where water is then
distributed, and those that can be practiced in individual homes.
Chlorination is the most common and effective method for purifying
water. Even under poor sanitary and hygienic conditions, in which people
collect whatever water that is available from community tanks, wells, pumps
and taps for use in their homes, if water is chlorinated, a dramatic decline in
the incidence of water-borne diseases follows.
The island-cluster nation of Maldives, in the Arabian Sea/Indian Ocean,
has developed an effective and inexpensive method for producing safe drinking
water that can be done at home. Called the solar water disinfection technique
(or SODIS), sunlight and plastic containers are used to kill pathogens
contaminating domestic water. More than a dozen solar water disinfection
techniques have been perfected and put into practice. A family, village or
community may choose the technique it finds most suitable to its
circumstances.
Simple ways to succeed: Some national examples
Seeking new sources of water often requires a great deal of effort and large
sums of money. As a result, such efforts must take place at the national or
transnational level. However, effective methods at the family and community
level can bring a rich supply of substantially clean water with little effort and
at a reasonable cost. Many countries have devised successful practices based
on this strategy. The most common method is water-harvesting, which involves
capturing rainwater and then using it to recharge groundwater sources and
refill collection ponds.
Nepal: This small Himalayan nation has always had a water problem. Its
population lives in far-flung isolated communities often on hillsides of varying
altitudes where rainfall occurs only 3 months a year. Pipeline water supplies
are neither easy to construct nor maintain. The Nepalese have developed
innovative microlevel methods to capture and harvest rainwater on rooftops,
soak pits and village ponds. Called Baresiko Pani Thapne, this communitybased rainwater harvesting scheme has eased water-shortage problems in
several districts in an economically efficient manner that also empowers
people by encouraging them to participate in the process.
13
Safe Drinking Water: The need, the problem, solutions, and an action plan
Sri Lanka: This pearl on the Indian ocean has a long-standing tradition of
harvesting rainwater using palm leaves, trees trunks and rocks. Gutters, made
of tin sheets, split bamboo, banana stems or arecanut sheaths, channel water
onto rooftops where it is captured and stored. Studies suggest that households
in the Anuradhapura District collect rainwater on rooftops not only because
it is economical but because of the rainwater’s incomparable quality.
Kenya: This lush equatorial country of great geographical contrasts has a
national rainwater association. In Laikipia, the association first harvested rain
in 200-litre drums but eventually turned to megalitre drums with capacities
ranging from 50 to 100 cubic metres. Such large storage capacities proved
sufficient for meeting human and livestock needs as well as the needs of
small-scale vegetable farms. Coupled with the runoff created by terraced
agriculture, the effort has helped to increase the efficiency of water harvesting.
These advances, which have taken place within the past 10 years, have
significantly raised agricultural productivity and living standards.
Ghana: The Ghana Water and Sewerage Corporation (GWSC), established
in 1965, works with nongovernmental organizations, individuals and
communities to provide safe, potable water by effectively tapping groundwater
and surface water sources. Methods are similar to those used in Kenya. The
GWSC-sponsored National Water Supply Programme provides water to about
60 percent of the 56,000 rural communities under its jurisdiction.
Indonesia: Dean Desa, a nongovernmental organization in this archipelago
nation, encourages public participation in the development and wise utilization
of water. Under a unique system of finance, affordable rainwater storage
cisterns can be built even in the poorest communities. The system works like
this: A family is given two female goats. When these goats bear four young
goats (which is often the case), two of the goats are returned to the owner
and two are given to the borrower. The borrower then rears the goats and
uses them as payment for water tanks. The Philippines have adopted the
same financial practice using hogs instead of goats as their medium of
exchange.
Singapore: This tiny nation pursues the world’s most comprehensive and
multi-faceted strategy for capturing rainwater for human use. The effort, which
is well-planned, easy-to-execute and cost-effective, could help solve watershortage problems faced by many other cities. Each high-rise building is
required to have a rooftop collection system. Water that is collected is sent to
two tanks, one of which is used solely for toilet flushing. Mosquito infestation
14
Making wastewater fit for use again
is controlled by fine mesh screens covering the tanks and dousing the stored
water with a paraffin oil layer. In addition to apartment houses and highrises, all educational institutions are required to collect, filter and chlorinate
roof top rainwater. The airport has been turned into another huge catchments
area. Runoff from rooftops, runways and hangars at Changi Airport provides
80,000 cubic metres of water. Computer analyses indicate resource savings
of more than 14 percent. Rainwater, moreover, costs nearly 25 percent less
than potable water to collect and distribute.
India: The sprawling desert province of India Rajasthan offers one of the
most successful efforts in harvesting and using water to meet community
farming and family needs. We highlight it for two reasons. First, many areas in
Central and West Asia have remarkably similar geo-climatic conditions to
those in Saharan Africa, which makes the experience in Rajasthan both relevant
and replicable. Second, the experience showcases an example in which the
‘technical solution of an urban engineer’ – characterized by digging deeper
borewells and using hand pumps – has been replaced by the ‘commonsense’
and ‘rural wisdom’ of local participants. Nongovernmental agencies recruited
people from some 150 remote rural schools and 50 community centres located
in dry or brackish water areas. After considerable interaction with and input
from the villagers, more than 200 underground tanks were constructed during
the ensuing decade using local labourers and materials. The initiative, which
employed 6,000 people, provided an additional 12 million litres of collected
rainwater upon its completion. Maintenance problems, which plagued the
piped-water and hand-pump system, are now few in number. These communal
tanks and wells, moreover, serve as a meeting place for rural women who
come there not only for water but for news, gossip and a guilt-free respite
from their men and families. In eastern Rajasthan, a rain-fed land, a
nongovernmental organization, Tarun Bharat Sangh, has helped local people
build 4,500 check-dams and water-harvest facilities in 850 villages using local
money and expertise. This effort has raised well levels 2 to 3 metres and
turned seasonal rivulets and tributaries into perennial sources of water for
some 100,000 people. In 2000, project leader Rajendra Singh, won the Ramon
Magsaysay Award for his efforts.
Making wastewater fit for use again
The examples cited above describe effective methods for harvesting water
and improving aquifer levels. Such efforts, in turn, make it possible to recharge
15
Safe Drinking Water: The need, the problem, solutions, and an action plan
groundwater aquifers. Another source of water that has the potential to be
recycled and made fit for consumption is wastewater. If left unrecycled,
wastewater returns to earth either directly or as a result of evaporation. Under
such circumstances, pollutants – if not recovered, controlled or treated –
remain a source of contamination, usually near the location where the water
is discharged. Consequently, recycling wastewater involves the removal and,
if necessary, recovery of pollutants. Two pilot projects in Sri Lanka and Chile
are worthy of discussion.
Sri Lanka: Sri Lanka extracts raw rubber from its rubber plantations and
then processes it for use in a variety of value-added products. The nation also
has vibrant coconut and textile processing sectors. These economic
endeavours generate considerable wastewater effluents that can be treated
and used again. To this end, the Rubber Research Institute built a pilot plant
capable of treating 30 cubic metres (30 million litres) of effluent water each
day. The system consists of (1) a ‘matter trap’ with five compartments that
lengthens the pathway through which the water must pass; (2) an anaerobic
digestion chamber with five compartments that holds and handles two days’
worth of effluent in a vented rectangular tank. There, colonized anaerobic
bacteria, which are found in the rubberized coconut fibres that fill the tank,
convert dissolved organic pollutants into gas (methane, hydrogen sulfide and
carbon-dioxide) – some 40 cubic metres of gas per 2 tons of rubber per day;
(3) the outflow then returns to the aerobic tank where the biodegradable
pollutants are digested in the presence of bubbled air; (4) the aerobically
treated effluent is fed into a circular conical floored clarifier enabling the
solids to settle into a sludge at the bottom. The effluent, meanwhile, flows
from the clarifier’s water surface into (5) a sand-bed filter consisting of sand
at the top and ‘metal’ gravel and stones of increasing size below. The filtered
liquid is subsequently discharged for reuse. Three such plants have been in
operation since 1995 and the process has now been licensed to a commercial
firm that plans to market it.
Chile: The operational scales and methodologies used in Chile differ from
those in Sri Lanka. The two-step Chilean technique, based on an aerobic
process, is more suitable for the treatment of sewerage generated at domestic
rather than industrial sites. The first step relies on a biofilter through which
the wastewater is drained. This filter consists of several layers with large stones
on the bottom, smaller stones and gravel above, followed by a layer of sawdust
– all of which is topped by 20 to 30 centimetres of humus containing a large
number of microorganisms and 5,000-10,000 earthworms per square metre.
The wastewater passing through the biofilter becomes clear as its original
16
Technologies to make safe drinking water
organic content is drastically reduced. Because the process is aerobic, the
larger the area and greater the aeration, the more effective it is. In the second
stage, water is processed through a shallow chamber where it is irradiated
with ultraviolet (UV) radiation from a UV-lamp delivering 30 watts per square
meter per second. Such UV intensity kills all the bacteria in the water within
one minute. Water exiting the UV chamber is not only sterile but of excellent
quality. The bio-reactor can handle up to 1,000 litres a day per square metre.
The system, moreover, is easy to maintain and does not consume a great
deal of electricity. Because residues do not accumulate, the only regular
maintenance consists of adding sawdust to the biofilter every few months.
Some humus should also be removed periodically to maintain an active and
growing biosystem. The system has been patented and commercially installed
in several different sites in Chile – for example, in schools with several hundred
students, settlements with 500 to 1,000 peoples, and even in a region with
12,000 people.
Private industry initiatives: In addition to national initiatives, private industry
has financed and implemented several comprehensive programmes to
improve the water quality of lakes, recycle water, and make potable water
available to villages (for example, Unilever’s PAGER programme Morocco).
The ‘Plebys’ initiative in the United States has developed a simple two-stage
filter (similar to the Chilean type) for use at home. Such programmes have
encouraged community participation, sometimes with small financial
incentives (for example, a few cents a day to pay for the materials and water
supply). Nongovernmental organizations have turned to local talent, resources
and institutional know-how to make safe drinking water available on consistent
basis.
Technologies to make safe drinking water
Unless water is made safe for drinking, the war against water-borne diseases
will be lost. Several convenient and easy-to-use methods have been devised.
Some, which rely on high-technology, are more suitable for use at city/central
point treatment facilities. Others, based on more modest technologies, can
be used at the settlement cluster level – in schools, community centres,
apartment buildings and villages. Then there are ‘traditional’ and/or
‘appropriate’ technological options that can be used in individual homes or
during emergencies. The quality of water obtained by each of these techniques
(high-, medium- or traditional- and appropriate-technology) should be
17
Safe Drinking Water: The need, the problem, solutions, and an action plan
excellent – free from pathogens and toxins and as fit for drinking as water
sold commercially.
High-technology/high volume methods: Time-honoured methods of treating
high volumes of water to meet the demand of urban populations involve
sedimentation and filtration followed by the killing of pathogens through
chlorination or sometimes ozone bubbling. While such processes remain
logistically feasible and even acceptable for relatively low-volume demand
(for example, in schools, hospitals and villages), these methods contend with
‘flow through’ or ‘steady-state’ volumes of water and not static captive pools
of water collected in siphoned tanks. To addresses these challenges, several
methods have been successfully devised and developed. A few are highlighted
below.
• UV-protected granulated activated charcoal bed: This innovative
method has been developed at the U.S. National Aeronautics and Space
Administration (NASA) Johnson Space Center. Charcoal is an effective waterpurification material that can adhere (adsorb on its surface) diverse classes
of inorganic, organic or biological contaminants. The larger the surface area
of the charcoal, the more effective it is. As a result, experts have opted to use
powdered or granulated charcoal instead of charcoal lumps. The process
extends the active life of the charcoal through the use of ultraviolet light that
inhibits the growth of microbes on the carbon surface while disinfecting and
purifying the water passing through the tubing. Unlike chlorinated disinfectants,
UV light does not leave residual matter, which helps to prolong the life of the
active charcoal bed.2
• Titanium dioxide and UV light as the purifier: More than 20 years
ago, Japanese scientists illustrated that anatase, a naturally occurring mineral
that is a form of titanium dioxide or TiO2, is an efficient disinfectant when
subject to ultraviolet radiation. Under such conditions, TiO2 produces reactive
oxygen and free radicals that kill bacteria, fungi and viruses in a brief time.
TiO2, a mineral found in abundance in nature in its purest raw form (in Africa,
Australia, Sweden and Canada), has been used as a whitener in paints, toothpaste, cosmetics and paper. The addition of TiO2 and the shining ultraviolet
rays (similar to the Chilean experience cited above) purifies the water though
‘photocatalysis’ (photo refers to the UV light; catalysis refers to the fact that
TiO2 aids the purification process without being used up). A decade ago, the
first International Conference on TiO2 Photocatalytic Purification and
Treatment of Water and Air, highlighting the advantages of using TiO2 and
UV-light to purify, took place in Canada. Since that conference, several
improvements have made the TiO2 photocatalysis method even simpler and
more effective.
2
For additional information, see www.usrttc.org/PDF/TBQ298.pdf
18
Technologies to make safe drinking water
• TiO2 and sunlight to purify water: While TiO2 is an inexpensive and
non-toxic substance used to purify water, it does have some disadvantages.
First, because it is suspended as a powder in water, it must subsequently be
filtered. Second, TiO2 uses ultraviolet light and most of the sun’s light that
falls on earth is above this range. To solve these drawbacks, a research team
in Germany sought to immobilize the catalyst as coatings on glass using a
process (sol-gel transformation) that produces solids from liquid solutions.
Such coatings could be used as effectively and for longer periods without
filtering. The researchers improved the light absorption character of TiO2 by
adding small quantities of iron oxide (Fe2O3) into the TiO2 grid. This allowed
the use of direct sunlight instead of UV-light. In experimental tests, the
composite TiO2 (Fe2O3 catalyst coated on glass), together with the use of
sunlight, proved successful, opening the possibility of much broader use.3
• Electrochemical activation (ECA): In this method, electrical energy
instead of light is used for purification. The catalyst is not TiO2 alone, but a
mixture of oxides of various metals (such as Ru, Ir, Pt and Ti) that are coated
on the surface of electrodes. The electrodes are placed on either side of a
vessel that is divided into two sections by a vertical diaphragm (ceramic,
coated with other oxides) which separates the water contained in the two
chambers. Rain water passes through one of these anode chambers to a
second vertical chamber that contains replacement-free and regenerationfree catalyst granules. The latter oxidizes all organic and biological substances
and decontaminates the water. The outflow is then fed into the other chamber
of the electrolytic column, while a direct current electrical energy, generated
by car battery, passes through. The electrochemical activation (double layer
intensification) is intense enough to purify even the most obdurate pollutant.
A business group from Estonia has commercialized the purifier as a low cost,
easy-to-maintain purification device that provides drinking water which meets
World Health Organization (WHO). The system yields 120 litres per hour,
consumes small amounts of energy and the cartridge does not have to be
replaced for years.4
• Portable reverse osmosis water purifiers: Commercial companies now
make small reverse osmosis devices for home use that can regularly produce
7 litres per hour of pure water from any type of water. The devices, which can
be mounted on a wall, consume little electricity, use membranes that do not
need replacement for 2 to 3 years, and rely on filters that must be replaced
just once a year. Home units currently cost US$200. Larger units, designed
to serve an apartment building with throughput rates of 100 litres per hour,
cost US$4000. These devices may prove attractive for middle- and upperincome homes or communities where water is hard or brackish.
3
4
For additional information, contact [email protected]
For additional information, see www.aquastel.com/summary.html
19
Safe Drinking Water: The need, the problem, solutions, and an action plan
• Efficient adsorbent filters: Filtering water removes suspended
particulate matter. The finer the filter, the more it can decontaminate and
purify. Use of a membrane allows selective passage of water while preventing
unwanted dissolved material from passing through. Water purification requires
a quick-flow, corrosion-resistant, high-stability (in terms of pressure,
temperature and contaminants) bactericidal and economical membrane filters.
Recent research in Russia on such filters has been promising. Laboratory
materials not have only met technical requirements but have been inexpensive
to produce, suggesting that it could suitable for domestic community and
industrial uses.5
Appropriate technologies for home use: In isolated rural communities in
developing countries and during emergencies, there should be access to rapid
but reliable methods of purification that supply small volumes of water (10 to
1,000 litres). The systems should rely as much as possible on local labour
and material. Use of alum, permanganate and chlorine tablets for quick
purification is easy and practicable at the domestic level.
A well-known and safe method practised at
homes in South Asia involves a mud-pot
filtering system (fig. 3). The top pot contains
pre-washed gravel and sand through which
raw water passes. The water exits through a
hole in the bottom of the pot into a second
pot kept below. The mouth of the second
pot is covered with a cloth filter while a
crushed coal bed lies on a pad below,
removing many toxins and germs from the
water. Clean water exits through a hole in
the bottom of the second pot and then is
collected below in a third earthenware pot.
The collection rate is slow, but it can be done
overnight at home so that clean, cool
drinking water is available throughout the
day. This method needs no electric power,
filters or chemicals. As a result, maintenance costs are minimal, requiring
only funds for the charcoal, gravel and sand that must be replaced every few
days.
Fig. 3 Mud-pot filtering system
The solar disinfection method (or SODIS) is an easy, small-scale and costeffective technique for providing safe water at homes or in small communi5
For additional information, contact [email protected]
20
Action plan
ties. Water is filtered to Fig. 4 Solar disinfection method
remove the solids and
particulate matter. The
water is then moved
into a throw-away, colourless and transparent
bottle where it is kept in
the sun for irradiation.
To maximize the effectiveness of the process,
the bottle should lie on
Inactivation of microorganisms
the ground and its surRemoval of solids
by UV radiation and thermal
face should be blackby sedimentation
treatment
ened to better absorb
the light and generate
heat (fig. 4).
The combination of solar radiation and heat inactivates pathogens. The
treated water can now be stored in a cool mud pot for drinking. This method
has been successfully tested in Bolivia, Burkina Faso, China, Colombia,
Indonesia, Thailand and Togo.6 In places where electric supply is available,
filter cartridges (with or without irradiation) can be used either on stored or
flow-through water supplies.
Action plan
Prospects for providing adequate access to safe drinking water to homes and
communities on a global scale may not be grim as we think. Ongoing efforts
by communities, townships, state, provincial and national governments have
made safe water a realizable goal. This is the theme of the Africa 2000 Initiative
for Water Supply and Sanitation, launched by World Health Organization
(WHO), in 1993. The effort led to the Brazzaville Declaration 1996, which
established relevant principles and recommendations for enabling the people
of Africa to have access to safe water supplies and sanitary waste disposal
facilities.
Individuals and communities. Efforts need not be left solely to governmental
and nongovernmental agencies. Individuals, families and communities also
have a vital role to play. Such responsibilities include:
• Water harvesting at home, schools and community buildings.
6
For further details, contact [email protected]
21
Safe Drinking Water: The need, the problem, solutions, and an action plan
• Water recycling at the microlevel, including at homes, buildings and
communities.
• Saving water by ensuring taps and pipes are not leaky and by using
optimum amounts of water for washing and toilet flushing.
• Making sure that the water is purified by methods suited to family
conditions and needs.
• Maintaining proper levels of sanitation at home.
Governments. Participants at the Second Regional Meeting on the Africa
2000 Initiative, held in Harare, Zimbabwe, agreed to a framework for action
and series of recommendations. While the efforts focused on Africa, the
recommendations and action plan could prove relevant for much of the world.
Based on these and other deliberations, and on the material discussed above,
we suggest the following action plan whose objectives are to (1) assist
countries in the formulation, implementation and monitoring of policies and
action plans designed to ensure safe water supply, and (2) to promote
cooperation among governments, international agencies, nongovernmental
organizations, and the private sector to advance the interrelated goals of safe
water and adequate sanitation. Major areas of focus include community
empowerment and management, private-sector involvement in water supply
and sanitation, country-level collaboration and cooperation, and sanitation
and hygiene education.
The action plan should include:
• Encouragement of political commitment through effective policy
formulation, support for the implementation of plans, and improved
budgetary allocations.
• Promotion of intersectoral coordination and cooperation to forge a
policy consensus for the promotion of safe water drinking.
• Support of local efforts and community-based strategies for
addressing the issue.
• Facilitation of access to appropriate technologies.
• Development of legal and regulatory frameworks for private industry
and nongovernmental participation.
• Devising of mechanisms that enable governmental agencies to pursue
sanitation as a national priority, including development of sanitation
policies and guidelines, organization of advocacy campaigns focusing
on policy makers, and the integration of hygiene education into all
water supply and sanitation projects.
• Involvement of women in water-supply activities by identifying
women’s groups and movements at all levels and incorporating their
22
Action plan
views into community-level water-harvesting, recycling, saving and
purifying, and supply initiatives.
Private industry and nongovernmental organizations. Many countries –
for example, India, Indonesia, Kenya, and Nepal – have active nongovernmental organizations that involve communities in the funding and
implementation of programmes designed to transform arid and semiarid
terrains into productive agricultural regions receiving sufficient amounts of
water. Such efforts should be expanded by:
• Exchanging information among and between industry and
nongovernmental organizations on relevant and novel methods and
strategies.
• Focusing on sociological factors that may have an impact on the
most suitable technologies and programmes for a given region/
community.
• Ensuring equity in both services and benefits.
• Involving communities in all aspects of water harvesting, recycling,
storage, purification and supply.
• Coordinating efforts among governmental and intergovernmental
sectors for the purposes of achieving harmonious processes and
results.
The proverbs “waste not, want not,” “little drops of water make the mighty
ocean,” and “what is saved is what is earned” represent simple truths. Water
is plentiful. What is needed is to ensure that it is not wasted but treated,
purified and made available in a fair and safe manner. The task is doable,
thanks to the earth’s hydrological cycle. The earth does not let a drop of
water escape but wraps it tightly within and around itself. We who live on
earth can – and should – do so too.
23